Drug residues have been detected in human hair specimens by a variety of analytical techniques. These reports have generated substantial interest in using hair as a historical record of drug usage. Studies are designed to determine the presence and time course of drugs of abuse in human hair. Healthy male volunteers with a history of chemical substance abuse will participate in the study. Informed consent will be obtained and all procedures will be approved by the hospital Institutional Review Board. Subjects will reside on the clinical ward of the ARC. Head and facial hair specimens will be obtained prior to and after administration of drugs of abuse. Blood, saliva and urine specimens also will be obtained. Analyses of tissue and biofluids for drug will be performed by radioimmunoassay and gas chromatography/mass spectrometry. The studies will provide the scientific basis for determining the usefulness of hair as a "historical record" for substance abuse.